1. Field of the Invention
The present invention relates to a technique for controlling the operation of a pump; and more particularly, the present invention relates to a method and apparatus for controlling and/or monitoring a pump, e.g., including for domestic and commercial heating or cooling water systems.
2. Brief Description of Related Art
In previous works for a hydronics pumping system sensorless control and monitoring by one or more of the inventors of the present application, a 3D sensorless converter was developed to obtain the system flow and pump differential pressure associated with any unknown hydronic pumping system, consistent with that disclosed in the aforementioned patent application Ser. No. 14/091,795. With the 3D sensorless approach, the system pressure and flow rate can be resolved directly from any pair of motor readout signals, such as speed, current, torque, power, and so on so forth, with high conversion accuracy. Consistent with that disclosed in the aforementioned provisional patent application Ser. No. 61/858,237, self-calibration sensorless adaptive pump control methods for hydronic pumping control systems were developed as well based upon the aforementioned 3D sensorless converter and adaptive control approaches disclosed in the aforementioned patent application Ser. Nos. 12/982,286 and 13/717,086. Following the approach, the adaptive pressure set point pumping control can be achieved with respect to dynamic hydronic system variation without a need for any pressure or flow sensors for pumping control.
Sensorless calibration instrumentation and data acquisition are always an interesting part of discussions regarding sensorless applications and not easy to be achieved for some applications due to lack of a pressure sensor or a flow meter in field, not to mention wiring issues. For some of the hydronic pumping applications where the flow rate monitoring is not very critical for pump control, however, a theoretical and discrete model without a need for instrumentation calibration may be easier to be used in the field.
There are several approaches that may be used for the sensorless conversion, including the discrete models calibrated with the pump and system hydronic data together with the numerical solutions. By way of example, see patent application Ser. No. 14/091,795, filed 27 Nov. 2013, entitled, “3D Sensorless Conversion Means and Apparatus for Pump Differential Pressure and Flow,” which is hereby incorporated by reference in its entirety. The discrete sensorless modeling approaches are simple and straight forward. The conversion accuracy may be preserved well with <5-10% margin of error if the conversion algorithm is well formed and calibrated properly. On the other hand, the theoretical sensorless model approaches may be formulated as well for some simple and easy pump control applications where there is no accurate flow and pressure requested for pump control and there may be the lack of calibration sensors. As a tradeoff, the flow and pressure conversion accuracy may have as low as a >10-15% margin of error. The conversion accuracy may be deteriorated very rapidly at low speed.
By way of example, FIG. 1 shows a water booster pumping system that is known in the art. FIG. 2 schematically shows the energy conversion between pump differential pressure and the flow rate associated with the equivalent hydronic system characteristics at the discharge section of a pump and the motor power and speed at the other end of a motor drive at any time. FIG. 3 schematically presents pump and system characteristics curves and an equilibrium point associated with pump differential pressure and system pressure.
Recently, issues regarding energy saving and environmental protection in such pumping systems have been addressed dramatically. Increasingly more attention is being paid to hydronic pump control applications, including pump controls for domestic and commercial heating and cooling water pumping or circulating systems, water booster pumping systems, and so forth, like those shown in FIG. 1 with their characteristics that may be dynamic and unknown in nature. For example, to reduce energy consumption and operation costs, the aforementioned adaptive control approaches have been proposed.